Re: XQuery question

> >> Given meta-data tables that describe relations between tables, [...]
>
> > Since the relational data model (rdm) defines a "relation" as being a
> > set of tuples which is generally conceptualized as a table, the above
> > sentence in rdm-speak would translate to "tables between tables" which
> > is probably not what you meant. What word did rdm formally assign to
> > the word "relation" as used in the above sentence? Surely rdm has a
> > formal word for that very basic and fundamental concept.
>
> He's obviously talking about entity tables and relation tables. See
> any text on the ER (entity-relationship) model for more information.

It is true that some relations are joined by having their foreign keys in a mapping relation that relates entities from two relations, and so in that case we could say "a relation between relations". But what about the case where there is no mapping relation involved between two related relations. For example:

T_Car
CarID
ColorID

T_Color
ColorID
Name

Here there are no relations between relation T_Car and T_Color. Some might say T_Car has a "relation" to T_Color but this would not make sense in rdm-speak since a relation is defined as "a set of tuples". What formal word has rdm defined to described this type of "relation" between T_Car and T_Color? Received on Mon May 19 2003 - 23:07:35 CEST